/*! \page siesta2qmcDoc Siesta to qmc


\section description Description

Basic usage: siesta2qmc [-siesta2] [-molecule]  [-analyze_mo] -o [outputroot]  [siesta output file] <br>

If outputroot is not given, it will default to qwalk.


\subsection options Options

The following options are required for the converter to work:
<pre>
\%block WaveFuncKPoints
0.0 0.0 0.0
\%endblock WaveFuncKPoints
LongOutput .true.
LatticeConstant 
</pre>

You need the lattice constant variable even if you're calculating
a molecule, since Siesta apparently doesn't print out the orbital
coefficients unless the lattice constant is given explicitly.  If you
are doing an actual molecule, you may want to change PERIODIC in the
QWalk .sys file to MOLECULE, which will increase the speed and accuracy.
The converter will attempt to do this automatically, but you can force it
with the option -molecule.  Be careful that the molecule does not depend on 
periodic boundary conditions!

The converter also supports non-gamma k-points, which can be printed out in the
Siesta input file as following:
<pre>
\%block WaveFuncKPoints
0.0 0.0 0.0
2.0 0.0 0.0
0.0 2.0 0.0
0.0 0.0 2.0
2.0 2.0 0.0
0.0 2.0 2.0
2.0 0.0 2.0
2.0 2.0 2.0
\%endblock WaveFuncKPoints
</pre>
for example, for a 2x2x2 Monkhorst Pack grid.

\subsection pseudo Pseudopotential

One can use the pseudopotentials written for QMC, although they can be
quite a pain to convert for use in Siesta, since they are usually
written in a Gaussian expansion.  We are developing a converter to 
do this properly, however, please contact Lucas Wagner if you wish 
to use Gaussian-based pseudopotentials with SIESTA.

Current thought is that PBE psp's are
probably your best bet.  SIESTA
may have exact exchange in the future, in which case hybrid or
Hartree-Fock psueudopotentials may be better.  To be clear, the
pseudopotentials should be tested, by, for example, calculating
the binding energy of small molecules.


\subsection basis Basis set

You may find that you need to use a larger basis set than is typical for
Siesta.  It appears that a triple-zeta quality with polarization or better
is necessary.  If the basis set is too small, the variance of the local
energy is large, because the basis cannot describe the one-body
part of the wave function well enough.  For molecules, you may also
need to extend the cutoff radius of the basis functions significantly to
keep the variance down and the wave function accurate.

Experience has shown that the main issue with the Siesta basis is the
presence of kinks when a cutoff is applied.  To avoid this issue,
we suggest that you use the splitgauss basis type with a large cutoff, 
somewhere around 8.0 Bohr or more.  With this basis, it is possible to 
get results on par with plane waves or quantum chemistry Gaussian 
type basis functions.

\subsection Siesta version 2

The option -siesta2 activates Siesta version 2 mode.  

*/
